Broadband Wireless Access (BWA) devices may provide a convenient broadband access mode to users. At present, there are BWA devices based on private protocols and BWA devices based on standard protocols. BWA technology is developing rapidly presently. The technology for developing broadband metropolitan area access using wireless resources has a strong vitality and a broad market space.
Wireless spectrum resources are very precious. Especially for some areas not well planned or some license-free frequency bands, a plurality of base stations usually runs on the same channel. As a result, the signals of different base stations interfere with each other. Therefore, in order to coordinate the coexistence of each base station device under the same frequency band, especially, the coexistence of each base station device under license-free frequency bands, some coexistence mechanism among base station devices needs to be established.
In a coexistence base station system, it is usually required that the transceiving synchronization should be guaranteed among different base stations, in other words, it is required that the frame timing for sending and receiving a signal among different base stations should be aligned rigidly. Therefore, it may be ensured that the transceiving interference among stations near each other is avoided. For example, for base stations BS1 and BS2 in FIG. 1, if BS2 is receiving signals when BS1 is sending signals, severe interference will be laid by BS1 to BS2 on the receiving of signals from subordinate subscriber stations of BS2.
The basic structure of the coexistence base station is as shown in FIG. 2, including three parts: a wireless functional part, a wired functional part and a coexistence functional part (including a coexistence database). Each of the coexistence functional part and the other two parts has an interface. The wired functional part is connected to a wired core network or an access network, and is responsible for the transceiving and processing related to the wired communication. The wireless functional part is connected to an air interface, and is responsible for the transceiving and processing of the wireless communication. The wired functional part and the wireless functional part are in communication with each other.
The base station has two states, i.e., a normal working state and a starting initialization state. In a coexistence base station system, the base station is usually connected to a core network via a wired path, and may be communicated with the core network via a wire.
By taking the coexistence base station network shown in FIG. 3 as an example, the initialization process of a base station near several base stations in normal working state will now be discussed.
To better describe the corresponding background technology, the definition of a neighbor station will be introduced first. The neighbor station refers to base stations with a common coverage area having effective subscriber stations. For example, in the network shown in FIG. 1, BS1 and BS2 are near each other geographically and lie in the coverage area of the other, but because there are no effective subscriber stations in the common coverage area of stations BS1 and BS2, stations BS1 and BS2 are not neighbor stations. However, although the overlapped coverage area of BS2 and BS3 is small and BS2 and BS3 do not lie in the coverage area of the other, there are effective subscriber stations in the overlapped coverage area and interference will be laid to the wireless network of the other party, BS2 and BS3 are referred to as neighbor stations.
In FIG. 3, there are a plurality of base stations near starting base station SBS1, such as WBS1, WBS2, WBS3 and WBS4. Subscriber stations A and B exist in the common coverage area of WBS1 and SBS1, subscriber station C exists in the common coverage area of WBS2 and SBS1, and subscriber station D exists in the common coverage area of WBS3 and SBS1. Therefore, WBS1, WBS2, WBS3 and SBS1 are neighbor stations. Subscriber station G locates in the overlapped part of the coverage areas of base stations WBS1 and WBS2. Other subscriber stations E/F/H/I/J/K do not lie in the overlap area of base stations.
During the starting process or the periodic broadcasting process, a base station needs to broadcast an IP address or other equivalent contact address to all subscriber stations in the coverage area of the base station, and a subscriber station in the coverage area of the base station forwards obtained address information to a working base station to which the subscriber station pertains. After the working base station obtains the address information, the base station may be found on the wired network.
To solve the problem of coexistence base stations, neighbor stations need to negotiate with each other. When air interface resources are allocated, a base station will send data to subscriber stations in interference-free area using competitive air interface resources (such as time period and subchannel), and send data to subscriber stations in interfered area using dedicated air interface resources (such as time period and subchannel).
Therefore, to effectively use the air interface resources, an operating base station needs to know the interference status of subscriber stations of the operating base station all the time, and needs to know whether each subscriber station is interfered and by which base station the subscriber station is interfered. Moreover, when a new neighbor station nearby is started, the base station updates the interference status information of known subscriber stations.
A method for collecting interference status information of a subscriber station by a coexistence base station in the prior art is as follows. After a neighbor base station is started, the original working base station queries the interference status information of subordinate subscriber stations of the original working base station continuously. If interfered information of a subscriber station is detected, it is indicated that the subscriber station is interfered by the neighbor station.
The disadvantage of this method lies in that, the base station to which the subscriber station pertains is unable to determine which neighbor station the subscriber station is interfered by. Therefore, the base station is unable to optimize the resource configuration according to the obtained interference status information of the subscriber station. For example, in FIG. 3, WBS1 finds that subscriber station G is interfered, but is unable to determine which neighbor station subscriber station G is interfered by. The query mode employed in the method adds the communication flow on the air interface, and the establishment and update of the database for saving the interference status information of a subscriber station in the base station is not timely enough.
Another method for collecting interference status information of a subscriber station by a coexistence base station in the prior art is as follows. After a new base station is started, the base station goes into a normal working state and establishes a contact with a neighbor station, then the neighbor station requires the subscriber station of the neighbor station to perform an interference detection, therefore a mutual interference relationship is determined.
This method has the following disadvantages:
1. When a base station does not negotiate with a neighbor station, there are no other signals on the air interface for the subscriber stations in the coverage area of the base station to perform a test and identification. Therefore, if the base station transmits a signal on an air interface, the normal communication of the neighbor station may have been interfered.
2. The measurement and detection approach for dedicated air interfaces is not used within the base station's initialization phase in this method, and when other messages or signals defined to perform the interference test on the subscriber station, the system may be more complex, and the processing time may be longer and be less timely.